The Experts below are selected from a list of 7047 Experts worldwide ranked by ideXlab platform
Jorge O. Galante - One of the best experts on this subject based on the ideXlab platform.
-
The Bone-Implant Interface of Femoral Stems with Non-Circumferential Porous Coating. A Study of Specimens Retrieved at Autopsy*
The Journal of bone and joint surgery. American volume, 1996Co-Authors: Robert M. Urban, Joshua J. Jacobs, Dale R. Sumner, Christopher L. Peters, Frank R. Voss, Jorge O. GalanteAbstract:A histological study was performed of the bone-implant interface of fifteen titanium-alloy femoral stems with Porous Coating limited to three proximal areas that did not cover the full circumference of the device. The specimens were obtained at autopsy from ten cadavera at a mean of forty-six months (range, one to eighty-nine months) after the implant had been inserted without acrylic cement. The volume fraction of bone within the Porous spaces (the percentage of the Porous space that was filled with bone) and the extent of bone ingrowth (the percentage of the Porous-coated surface covered with ingrown bone that was more than one-half fiber-diameter deep, as measured from the outer surface of the Porous Coating), were determined with histomorphometric methods. Eleven of the fifteen stems had bone within the Porous Coating that was in continuity with the surrounding medullary bone. The mean volume fraction of bone ingrowth in these specimens was 26.9 per cent (range, 12.2 to 61.0 per cent), and the mean extent of bone ingrowth was 64.3 per cent (range, 28.6 to 95.2 per cent). Both of these parameters increased with time. In the other four stems, the bone lacked continuity with the surrounding trabecular bed. Two of these stems had a limited amount of bone within the Porous Coating, and two stems (from one patient) had no bone ingrowth. Periprosthetic membranes surrounded by a shell of trabecular bone covered the uncoated surfaces of the stems. The membranes of implants that had been in situ for eight months or more demonstrated polyethylene wear debris, and other particles generated at the level of the joint, within histiocytes throughout the length of the femoral stem. CLINICAL RELEVANCE: The findings in this study are relevant to the utilization and mechanisms of failure of femoral stems inserted without cement. Bone ingrowth and the resulting stability of the implant can be achieved with Porous-coated stems. However, the extent of the surface that is Porous-coated must be sufficient to prevent trabecular fracture as a secondary mechanism of loosening. Interruptions in the circumferential extent of the Porous surface are associated with the formation of periprosthetic membranes, which provide a pathway for migration of particulate wear and corrosion products to the distal part of the stem. A circumferential Coating may retard the access of particles and thus decrease the possibility of diaphyseal osteolysis.
-
determinants of stress shielding design versus materials versus interface
Clinical Orthopaedics and Related Research, 1992Co-Authors: Dale R. Sumner, Jorge O. GalanteAbstract:Experimental studies of cementless Porous-coated total hip arthroplasty indicate that a critical design variable for femoral remodeling is stem stiffness. In the long term (two years) in the canine model, other variables, including the presence, type, and placement of the Porous Coating, did not sig
Leo A. Whiteside - One of the best experts on this subject based on the ideXlab platform.
-
Effect of Porous-Coating configuration on tibial osteolysis after total knee arthroplasty
Clinical orthopaedics and related research, 1995Co-Authors: Leo A. WhitesideAbstract:Porous-Coating configuration on the undersurface of tibial components in total knee arthroplasty was evaluated for its effect on tibial osteolysis. Clinical data and radiographic results of 675 Ortholoc II components (range, 4-8 years postoperative) and 236 Ortholoc Modular components (range, 2-4 years postoperative) were compared. The undersurface of the Ortholoc II tibial component is completely covered with Porous Coating, and that of the Ortholoc Modular is partially Porous coated with smooth metal bridges connecting the 4 screw holes and joint cavity to the smooth metal stem. None of the radiographs of the Ortholoc II tibial components showed significant osteolysis around the stem or pegs. Radiographically detectable signs of osteolysis around the distal 1/2 of the stem appeared in 28 of the 124 long-stemmed Ortholoc Modular knees. None had radiographically identifiable osteolysis around the screws or pegs. In the 112 knees with short stems, 19 had radiographically identifiable radiolucency around the stem, but none had radiolucency around the screws or pegs. Despite their substantially shorter followup, cementless tibial components with patches of Porous Coating connected by smooth metal tracks were more likely to have osteolysis develop than those with uninterrupted Porous Coating on the undersurface of the tibial tray. The smooth metal tracks appear to conduct debris from the joint cavity to the areas surrounding the stem.
Bu-xuan Wang - One of the best experts on this subject based on the ideXlab platform.
-
Effect of nanofluids on thin film evaporation in microchannels
Journal of Nanoparticle Research, 2011Co-Authors: Jun-jie Zhao, Yuan-yuan Duan, Xiao-dong Wang, Bu-xuan WangAbstract:A thin film evaporation model based on the augmented Young–Laplace equation and kinetic theories was developed to describe the nanofluid effects on the extended evaporating meniscus in a microchannel. The nanofluid effects include the structural disjoining pressure, a thin Porous Coating layer at the surface formed by the nanoparticle deposition and the thermophysical property variations compared with the base fluid. The results show that the nanofluid thermal conductivity enhancement mainly due to the Brownian motion tends to greatly increase the liquid film thickness and the thin film heat transfer. The structural disjoining pressure effect tends to enhance the nanofluid spreading capability and the thin film evaporation. The nanoparticle-deposited Porous Coating layer improves the surface wettability while significantly reducing the thin film evaporation with increasing layer thickness due to the thermal resistance across this layer. The nanofluid thermal conductivity enhancement together with the structural disjoining pressure effect can not counteract the thermal resistance effects of the Porous Coating layer when the Coating layer thickness is sufficiently large.
William G. Ward - One of the best experts on this subject based on the ideXlab platform.
-
Animal model for evaluation of soft tissue ingrowth into various types of Porous Coating.
Clinical orthopaedics and related research, 2002Co-Authors: Douglas B. Freels, Scott E. Kilpatrick, E. Stanley Gordon, William G. WardAbstract:Results from several studies have suggested that soft tissue ingrowth into Porous Coating can serve as a biologic containment mechanism to prevent particulate debris migration by sealing off the effective joint space. Therefore, a rabbit animal model was developed to investigate soft tissue ingrowth into various types of metallic rods. After implantation of several types of coated and smooth rods within the thigh musculature of rabbits, a thick encapsulation of soft tissue was observed around Porous-coated rods whereas a nonadherent pseudosynovial-lined cavity was observed around smooth rods. Within 3 weeks, soft tissue had grown into the three different types of Porous Coating on the rods. Histologic evaluation verified that maturation of this ingrowth tissue occurred by 12 weeks. Incomplete soft tissue ingrowth occurred into the depths of large-bead (590-840 mm) Porous-coated surfaces. Soft tissue separation from the bead surfaces was observed at 12 weeks in the Porous-coated implants that also had been coated with a thin layer of tricalcium phosphate. These findings suggest that soft tissue ingrowth can be expected to occur into the Porous Coatings tested, but that tricalcium phosphate should not be used as an additional surface Coating to obtain long-term adherence of circumferential soft tissue ingrowth.
Joshua J. Jacobs - One of the best experts on this subject based on the ideXlab platform.
-
nanoscale surface modification by anodic oxidation increased bone ingrowth and reduced fibrous tissue in the Porous Coating of titanium alloy femoral hip arthroplasty implants
Journal of Biomedical Materials Research Part B, 2017Co-Authors: Deborah J Hall, Robert M. Urban, Robin Pourzal, Thomas M Turner, Anastasia K Skipor, Joshua J. JacobsAbstract:Hip arthroplasty femoral stems coated with Ti6Al4V beads were treated by anodic oxidation in H3 PO4 for enhanced bioactivity and were studied in a 6-month canine model to determine the effects of the treated surface on the ingrowth of bone and soft tissues. The area fractions of bone, marrow, and fibrous tissue in the Porous Coating of seven treated and seven untreated control implants were determined using histomorphological techniques. The area fraction of bone within the Porous Coating was greater for anodic oxide treated (23.6 ± 8.3%) compared to control implants (l2.7 ± 4.7%) (p = 0.013), and there was less fibrous tissue in the treated implants (18.0 ± 9.5%) compared to the controls (33.1 ± 7.9%) (p = 0.006). XPS, XRD, TEM, and SEM analyses of the treated implants revealed a 400 nm-thick titanium oxide layer of low crystallinity with an undulating surface, populated with more than 25 nm-size pores per square micrometer. There was no detectable increase in serum titanium or in generation of particulates locally compared to the control implants. Micro and nanoscale surface modification by anodic oxidation increased bone ingrowth and reduced fibrous tissue, which may extend the longevity of fixation, limiting pathways for particle migration, and impeding the progression of osteolysis and aseptic loosening of arthroplasty components. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 283-290, 2017.
-
The Bone-Implant Interface of Femoral Stems with Non-Circumferential Porous Coating. A Study of Specimens Retrieved at Autopsy*
The Journal of bone and joint surgery. American volume, 1996Co-Authors: Robert M. Urban, Joshua J. Jacobs, Dale R. Sumner, Christopher L. Peters, Frank R. Voss, Jorge O. GalanteAbstract:A histological study was performed of the bone-implant interface of fifteen titanium-alloy femoral stems with Porous Coating limited to three proximal areas that did not cover the full circumference of the device. The specimens were obtained at autopsy from ten cadavera at a mean of forty-six months (range, one to eighty-nine months) after the implant had been inserted without acrylic cement. The volume fraction of bone within the Porous spaces (the percentage of the Porous space that was filled with bone) and the extent of bone ingrowth (the percentage of the Porous-coated surface covered with ingrown bone that was more than one-half fiber-diameter deep, as measured from the outer surface of the Porous Coating), were determined with histomorphometric methods. Eleven of the fifteen stems had bone within the Porous Coating that was in continuity with the surrounding medullary bone. The mean volume fraction of bone ingrowth in these specimens was 26.9 per cent (range, 12.2 to 61.0 per cent), and the mean extent of bone ingrowth was 64.3 per cent (range, 28.6 to 95.2 per cent). Both of these parameters increased with time. In the other four stems, the bone lacked continuity with the surrounding trabecular bed. Two of these stems had a limited amount of bone within the Porous Coating, and two stems (from one patient) had no bone ingrowth. Periprosthetic membranes surrounded by a shell of trabecular bone covered the uncoated surfaces of the stems. The membranes of implants that had been in situ for eight months or more demonstrated polyethylene wear debris, and other particles generated at the level of the joint, within histiocytes throughout the length of the femoral stem. CLINICAL RELEVANCE: The findings in this study are relevant to the utilization and mechanisms of failure of femoral stems inserted without cement. Bone ingrowth and the resulting stability of the implant can be achieved with Porous-coated stems. However, the extent of the surface that is Porous-coated must be sufficient to prevent trabecular fracture as a secondary mechanism of loosening. Interruptions in the circumferential extent of the Porous surface are associated with the formation of periprosthetic membranes, which provide a pathway for migration of particulate wear and corrosion products to the distal part of the stem. A circumferential Coating may retard the access of particles and thus decrease the possibility of diaphyseal osteolysis.